Circuit interrupters



Jan. 31, 1961 M. E. REAGAN CIRCUIT INTERRUPTERS 5 Sheets-Sheet 1 Filed Jan. 22, 1957 INVENTOR Maurice E.Reagun WITNESSES ATTORNEY 31, 1961 M. E. RE.AGAN 2,970,196

CIRCUIT INTERRUPTERS Filed Jan. 22, 1957 5 Sheets-Sheet 2 Fig.4.

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Normal Anode Current Pulses Time Current Thru Arcing Tips and Blowing Coils Time Typical Current Pulses Jan. 31, 1961 M E. REAGAN 2,970,196

CIRCUIT INTERRUPTERS Filed Jan. 22, 1957 5 Sheets-Sheet 4 Jan. 31, 1961 M. E. REAGAN 2,970,196

CIRCUIT INTERRUPTERS Filed Jan. 22, 1957 5 Sheets-Sheet 5 Fig.H.

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CHRCUIT INTERRUPTERS Maurice E. Reagan, Forest Hills Boro, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Jan. 22, 1957, Ser. No. 635,401

3 Claims. (Cl. 200-447) This invention relates to circuit interrupters in general, and more particularly, to arc-extinguishing structures therefor.

A general object of the present invention is to provide an improved circuit interrupter which will effect extinction of the are more quickly than has been attained heretofore.

Another object of the invention is to provide an improved circuit interrupter having means for more quickly building up the magnetic blowout flux than circuit interrupters heretofore used.

A more specific object of the present invention is to provide an improved circuit interrupter in which inductance is associated with the main contacts so that during the occurrence of a steep wave front of fault current, this inductance will force the current to take a parallel path through a blowout coil structure to more quickly build up the magnetic field and to bring about are extinctio n.

Still another object of the present invention is to provide an improved circuit interrupter in which one or more serially related potential coils are disposed upon the magnetic circuit of the blowout structure, which potential coils are connected to the terminals of the circuit interrupter. For direct-current service, a capacitor in series with the one or more potential coils may be used to halt the current in the fully open-circuit position of the interrupter. For alternating-current service, a series auxiliary switch may be used, which opens when the interrupter opens.

' Further objects and advantages will readily become ap parent upon reading the following specification, taken in conjunction with the drawings, in which:

Figure 1 is a side elevational view, partially in section, of a direct-current circuit interrupter embodving the principles of the invention and shown in the closedcircuit position;

Fig. 2 is a fragmentary, vertical, sectional view taken substantially along the line 11-11 of Fig. 1 illustrating the U-shaped iron washers about the main conductor stud of the interrupter illustrated in Fig. 1;

Fig. 3 is a diagrammatic representation of the circuit interrupter illustrated in Fig. 1, with many of its parts omitted, to more clearly illustrate the manner of operation, the contact structure being shown in the initial stage of the opening operation;

Fig. 4 is a perspective fragmentary view illustrating the holding-coil arrangement for maintaining the circuit interrupters of Figs. 1-4 in the closed-circuit position;

Fig. 5 illustrates the loss of time in a conventional direct-current circuit interrupter in building up sufficient arc voltage for interruption, and on the same time scale indicating the rise of fault current on a conventional type direct-current circuit interrupter;

Fig. 6 is a diagrammatic representation of the normal anode current pulses through the direct-current circuit interrupter of Fig. 1, as applied to a mercury arc rectifier system. This figure also diagrammatically represents on Patented Jan. 31, 1961 the same time scale, the current through the arcing tips and blowout coil of the circuit interrupter of Fig. 1 as a result of the aforesaid normal anode current pulses;

Fig. 7 is a side elevational view through a modified type of direct-current circuit interrupter utilizing a plurality of potential coils about the magnetic circuit of the blowout magnet, the contact structure being illustrated in the closed-circuit position;

Fig. 8 is a fragmentary diagrammatic view of the direct-current circuit interrupter of Fig. 7, the contact structure being illustrated during the initial portion of the opening operation;

Fig. 9 is a diagrammatic representation of the arcvoltage characteristics according to a conventional directcurrent circuit interrupter;

Fig. 10 is a diagrammatic view showing the improvement over Fig. 9 resulting from an application of the potential coils of the invention in speeding up the increase in arc voltage during the opening operation; and

Fig. 11 illustrates a side elevational view, partially in section, of an alternating-current circuit interrupter utilizing a potential coil connected through an auxiliary switch.

In the design of direct-current circuit interrupters, particularly in the higher current and interrupting ratings, it is important to accomplish the following:

(a) Start the breaker open as near to the time of the fault as possible.

(b) Start the lengthening of the are as fast as possible in order to produce enough arc-voltage to quickly force the fault current to zero.

(0) Clear the space between the moving and stationary contacts of any ionized gases so that a restrike cannot occur as the original arc is reduced to zero, even though the extinction occurs at the time of maximum recovery voltage.

A blowout coil is desirable to supply additional ampereturns forcing and controlling the lengthening and direction of the are into the deionizing arc-chute. If the blowout coil is permanently connected in the circuit, much larger copper turns are required which increases the size, cost and heatings of the breaker current-carrying parts. It is desirable to either have the blowout turns out in the circuit by the arc, or to have it normally short-circuited by the contacts as they part during the opening operation. The latter method is utilized in the present invention.

Another important point in direct current interruption is to quickly and completely shift the current from the main to the arcing contacts without burning the main contacts.

Referring to Fig. 1, which illustrates a direct current circuit interrupter, particularly adapted for the protection of anode circuits in mercury arc rectifier applications, it will be noted that there is provided a pair of main contacts 1, 2 which are shunted by a pair of arcing contacts 3, 4. The arcing contact 4 is insulated from the stationary main contact 1 by a plate of insulation 13a. The relatively stationary arcing contact 4 is connected through a connector 5 to an arc horn 6 and also through a lead 7 to one terminal of a blowout coil 8. The blowout coil 3 encircles the bight portion, or core 9 of a blowout magnet structure 10, comprising a pair of side pole plates 11, only one of which is shown in Fig. 1. The other terminal 12 of the blowout coil 3 is connected to the main contact stud 13 of the interrupter, to the righthand end of which are clamped disconnecting fingers 14. As illustrated in Fig. 1, the disconnecting fingers 14-, biased inwardly by a garter spring 15, engage a terminal stud 16, which may be associated with a cell structure, not shown.

The movable main and arcing contacts 2, 3 are carried by a rotatable contact arm 17, a biasing spring 18 being provided for furnishing the requisite contact pressure. The contact arm 17 is pivotally mounted about a stationary pivot 19 fixed to a bucking bar 20, which passes downwardly through a holding magnet 21. The lower terminal 20a of the circuit interrupter, as shown, constitutes an extremity of the bucking bar 20. With particular reference to Fig. 4, it will be observed that a holding coil 22 is provided, being energized from some suitable direct current source to set up a flux in the direction of the arrows 23 through the holding magnet 21, thereby maintaining the armature 24 in an attracted position. The armature 24 is pivotally mounted, as at 25, to a crank arm 26, the latter being pivotally mounted about a fixed pivot 27. The crank arm 26 has pivotally connected thereto a link 28, the upper end of which is pivotally connected to the knee joint 29 of a first toggle, generally desiginated by the reference numeral 30.

The first toggle 30 includes a pair of toggle links 31, 32. The toggle 31 has its right-hand end pivotally connected, as at 33, to the rotatable contact arm 17. The other toggle link 32 has its left-hand end pivotally connected to the knee joint 34 of a second toggle 35. The second toggle 35 includes a closing lever casting 36, the lower end of which is pivotally connected, as at 37, to a pull rod 38. The closing lever casting 36 is pivotally mounted about a fixed pivot 65 and has an opening 66 provided therein for the accommodation of a closing handle, not shown. The pull rod 38 is pivotally connected, as at 39, to the armature 40 of a closing solenoid, generally designated by the reference numeral 41.

With the circuit interrupter in the closed-circuit position, as illustrated in Fig. l, the second toggle 35 is over center, but is prevented from moving further by the compressive force present in the pull rod 38. The first toggle 30 does not go over center, but the toggle 3tl cannot collapse as long as the armature 24 is held by the mag netic attraction of the holding magnet 21. However, if the bucking-bar current reverses, or if the holding coil circuit is interrupted, the armature 24 will be released, and knee pivot 29 will move upwardly causing the first toggle 30 to collapse and the movable contact arm 17 will be opened by the compression spring 42 (Fig. 3). The knee pin 34 of the second toggle 35 remains nearly stationary until, the contact arm 17 is open. Then, it is moved upwardly by the retrieving Spring 43 (Fig. 3) disposed in the closing magnet 41.

The second toggle 35, as mentioned, is moved over center in the closed position of the interrupter, but is prevented from moving further by the compressive force present in the pull rod 38, when the closing solenoid plunger 40 hits the bottom of the closing magnet 41. This toggle can be closed or opened manually by inserting a maintenance closing handle in the closing lever casting 36 and raising or lowering the handle. In order to close the breaker, the armature 24 must be held by energizing the holding magnet coilv 22. If the armature 24 is not held, the first toggle 30 nearest the moving contact arm 17 will collapse and the breaker will open.

When the breaker does open, the main contacts 1, 2 will be separated prior to the arcing contacts 3, 4. When the arcing contacts 3, 4 do separate, the are drawn therebetween will move upwardly along the arc horns 6, 44 into engagement with a plurality of slotted, spaced, insulating plates 45, within which are extinction will soon occur. The blowout field set up between the two pole plates 11 by energization of the blowout coil 8 will assist in causing upward movement of the are along the arc horn 6, 44.

In the prior art type of high speed anode circuit breakers for heavy-duty rectifier service, the blowout coil is not connected into the circuit until the arc is lengthened to the point when one end of the arc impingeson" the end of the blowout coil terminal. This results in a loss of time in building up sufficient arc voltage to force the current toward zero. This rise in arc voltage is illustrated in Fig. 5.

The present invention proposes to add a plurality of iron laminations 46 (Fig. 1) about the main contact stud 13 to result in considerable inductance being associated with the main contact stud 13. Thus, there are two current paths in parallel, one through the main contact stud 13 and the other including the blowout coil 8, sincethe plate of insulation 13a insulates arcing contact 4 from the main stationary contact 1. When a fault occurs, and the steep wave front of fault current tends to divide equally in the aforesaid parallel paths, the current is rapidly shifted on the occasion of a steep wave front from the main to the arcing contacts 3, 4, because of the inductance associated with the iron plates 46 about the contact stud 13. Since the blowout coil 8 is in the arcing contact circuit, a powerful electromagnetic field is produced to stretch the arc and build up the necessary are voltage more quickly. Thus, the are drawn between the arcing contacts 3, 4 would be moved more quickly up into the arc chute 62 including the plates 45, and would be more quickly extinguished than if there is no associated inductance with the contact stud 13, as shown in Fig. 1.

In normal service, however, the lower resistance of the main contact path, including main contacts 1, 2 and the contact stud 13, will cause it to carry most of the current. Fig. 6 shows the relative current division during normal service.

As a result of the foregoing construction, the arc volt age will be built up more quickly, the current will be aided in transferring to the arcing contacts, the opening of the breaker will be speeded up, arcing time reduced, and less ionized gas will be produced between the contacts. Hence, more efficient operation is obtained.

Although the invention has been described in connection with a direct-current circuit interrupter used on a mercury arc rectifier system, the invention can, with act-- vantage, be applied to alternating-current circuit interrupters. It will result in the same unequal division of current upon the occurrence of a steep wave front.

Fig. 7 illustrates a modified form of the invention. The general method of operation and the overall structure is similar to that of Fig. l, and hence will not be repeated. Fig. 7, however, utilizes a plurality of serially related potential coils 63 connected through a capacitor C to the terminals 13, 20a of the interrupter. Fig. 7 only shows one potential coil 63 on one leg 11 of the magnetic circuit 10. Preferably, there are two such coils 63 connected in series, one surrounding each leg 11 of the magnetic circuit 10, and acting in such a' direction as to assist the magnetic action of blowout coil 8.

With direct-current circuit interrupters, itis desirable to have a blowout coil which is normally out of the circuit, and which is inserted in the circuit as the breaker opens. One means of doing this is to have'the arc cross an insulating gap and impinge on one end of the blowout coil.

As is well known, the blowout coil with its 'iron magnetic circuit produces an electromagnetic field which forces the arc upwardly. However, before the arc reaches the end of the blowout coil to insert it into the circuit, the only force driving the arc in the upward direction is the one loop through the breaker, including the breaker terminals. As a result, the arc voltage is slow in building up' until the blowout coil is inserted into the circuit. This'results in more ionized gas in the region between the contacts thus making it easier for the arc to restrike between them after the arc voltage has been built up to ahigh enough value to force the current downward to zero.

As a means of speeding up the interruption and reducing the temperature and amount ofionized gas" in the contact region, one or more potential'coils 63 are proposed to be added about the magnetic circuit 10,.

connected in'series so as to be in the same direction as that produced by the ampere-turns of the usual blowout coil 8.

As the contacts 3, 4 start to part, an arc is drawn, which increases in voltage drop as the arc lengthens. This increasing voltage is applied to the many turns of the auxiliary blowout coils 63, which are connected across the breaker terminals 13, 20a and a capacitor C in'series. The capacitor C helps to neutralize the inductance of the added blowout coils 63, lessens the time constant of the circuit, permits current of the right polarity to flow at the time it is needed for are stretching and serves as an insulator across the open breaker after the rate of change of arc voltage has gone to zero.

Fig. 9 shows the characteristic of arc voltage before the auxiliary potential blowout coils 63 are added. This would be the case for a conventional circuit interrupter, such as shown in Fig. 8 without the potential coils 63. Fig. 10, on the other hand, shows the changed arc voltage characteristics after the auxiliary blowout coils 63 are connected into the circuit.

Fig. 11 shows an application of the invention to an alternating-current circuit interrupter utilizing at least one of the potential coils 63. As shown in Fig. 11, a pair of terminal studs 68, 69 are electrically connected to the stationary and movable arcing contacts 70, 71. A blowout coil '72 is inserted into series circuit upon the arc contacting the arc horn 73. As shown, only one potential coil 63 is utilized, being connected across the terminal studs 68, 69 through an auxiliary switch 75. The auxiliary switch 75 comprises a pair of stationary fingers 76, which are bridged, in the closed-circuit position of the interrupter, by a rod contact 77 which is aflixed to a pull rod '78 through an insulating portion 79.

Thus, in the closed-circuit position of the interrupter, the potential coil 63 is connected through the closed auxiliary switch 75 to the terminal studs 68, 69. During the opening operation, the potential coil 63 is energized by the increasing arc voltage across the arcing contacts 70, 71, and this assists in building up flux in the magnetic circuit 30 in the same direction as does the blowout coil 72. Following are extinction, and movement of the pull rod 78 to the open-circuit position, the auxiliary switch opens and prevents any current flow through the potential coil 63 in the fully open-circuit position of the interrupter.

. From the foregoing description, it will be apparent that the use of a potential coil connected across the terminals of the interrupter may be applied not only to directcurrent circuit interrupters, but also to alternating-current circuit interrupters, providing suitablemeans are employed to halt current flow through the potential coil in the open-circuit position of the interrupter.

From the foregoing description, it will be apparent that there is provided an improved circuit interrupter having improved means for rapidly building up the magnetic blowout field. The potential coils 63 and the inductance 46 may be used on the same circuit interrupter. Merely for the purposes of clarity were they employed on different interrupters as described herein.

The invention has particular applicability to directcurrent anode circuit interrupters for use in mercury arc rectifiers, but the invention may be employed in any circuit interrupter, either alternating current or direct current, where rapid arc extinction is desirable.

Although there have been shown and described specific structures, it is to be clearly understood that the same were merely described for purposes of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

I claim as my invention:

1. A circuit interrupter for interrupting an electrical circuit including a relatively stationary main contact, a relatively movable main contact separable from said relatively stationary main contact to establish an are, a pair of separable arcing contacts, one of said arcing contacts being movable and electrically connected to the relatively movable main contact, means insulating the other relatively stationary arcing contact from the relatively sta tionary main contact, a terminal stud connected to the relatively stationary main contact, a blowout coil for creating a magnetic field for effecting movement of said established are, means connecting one end of the blowout coil to said relatively stationary arcing contact, second connecting means for connecting the other end of the blowout coil to said terminal stud, inductance means separate at all times from the electrical circuit and at no time carrying current, said inductance means being associated with the portion of the main current path through the interrupter between the relatively stationary main contact and said second connecting means to shift the steep wave front of fault current from the main to the arcing contacts and the blowout coil circuit, whereby the fault current is caused to shift extremely rapidly from the main current path through the relatively stationary main contact to the blowout coil circuit including the relatively stationary arcing contact.

2. A circuit interrupter for interrupting an electrical circuit including a pair of separable main contacts, a pair of separable arcing contacts, a terminal stud connected to one of said main contacts, a blowout coil, means connecting one end of said blowout coil to one of said arcing contacts and the other end of said blowout coil to said terminal stud, and magnetic means separate from said electrical circuit encircling said terminal stud between said one main contact and the connection of said blowout coil to said terminal stud.

3. A circuit interrupter for interrupting an electrical circuit including a pair of separable main contacts, a pair of separable arcing contacts, a terminal stud connected to one of said main contacts, a blowout coil, means connecting one end of said blowout coil to one of said arcing contacts and the other end of said blowout coil to said terminal stud, and magnetic washers separate from said electrical circuit encircling said terminal stud between said one main contact and the connection of said blowout coil to said terminal stud.

References Cited in the file of this patent UNITED STATES PATENTS 1,623,851 Paul Apr. 5, 1927 1,722,046 Fuller July 23, 1929 2,437,863 Scott Mar. 16, 1948 FOREIGN PATENTS 379,608 Germany Aug. 24, 1923 537.294 Germany Oct. 31, 1931 588,261 France Jan. 28, 1925 837,964 France Nov. 28, 1938 

